Tape recording apparatus and method

ABSTRACT

A tape recording apparatus is configured for sequentially recording files when receiving a command to write the files from an external host. The tape recording apparatus includes a buffer for temporarily storing the files, a tape on which the files are recorded, a writing device for writing the files stored in the buffer on the tape, and a writing control device for performing control of sequentially writing the files stored in the buffer on the tape one by one. The writing control device memorizes designated delimiter positions when delimiter position designation commands are received from the external host, the delimiter position designation commands designating the delimiter positions of the files to be sequentially written.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of JP 2006-333777, filed Dec. 11, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a tape recording apparatus,and particularly to a tape recording apparatus and writing controlmethod thereof with improved writing performance.

2. Description of Related Art

FIG. 1 shows a configuration 200 of a tape archive system (also referredto as “a tape backup system”) as an example of the configuration of atape recording system. On a tape cartridge 240 (hereinafter alsoreferred to as “a tape”), which is mounted on the tape drive connectedwith a computer (a host, a server, or a PC) 210, data recorded on a harddisk (HDD) 220 is archived. The tape cartridge 240 ensures high reliancefor a long period of time with low cost, when compared with otherrecording media such as an HDD, a CD, a DVD and a DRAM.

BRIEF SUMMARY OF THE INVENTION

The invention provides a tape recording apparatus for sequentiallyrecording files when receiving a command to write the files from anexternal host. In one embodiment, the tape recording apparatus includesa buffer for temporarily storing the files, a tape on which the filesare recorded, a writing module for writing the files stored in thebuffer on the tape, and a writing control module for performing controlof sequentially writing the files stored in the buffer on the tape oneby one. The writing control module memorizes designated delimiterpositions when commands (delimiter position designation commands) arereceived from the external host, the commands designating the delimiterpositions of the files to be sequentially written.

The writing control module notifies the external host of information onwhether or not the files have been written on the tape to the delimiterpositions when the delimiter position designation commands aresequentially received, and also when a command (writing position checkcommand) to check up to which delimiter position the files have beenwritten on the tape is received.

The invention also provides a tape recording system, which includes saidtape recording apparatus connected with a host. The tape recordingsystem is configured for receiving a command to write the files anddelimiter position designation commands for delimiter positions of thefiles, which are issued by the host.

In one embodiment of the tape recording system, the writing controlmodule memorizes sequence numbers indicating an order of receiving thecommands as designated delimiter positions when the position designationcommands are sequentially received.

When the position designation commands are sequentially received, andalso when a command to check up to which delimiter position the fileshave been written on the tape (writing position check commands) isreceived from the external host, the writing control module notifies theexternal host of information on whether or not the files have beenwritten on the tape up to the delimiter positions.

In response to the writing position check commands, the writing controlmodule notifies the external host of the sequence number indicating thelast written delimiter position on the tape as information on whether ornot the files have been written on the tape up to the designateddelimiter positions.

In response to the writing position check commands, the writing controlmodule notifies the external host of a relative value of the sequencenumber of the last written delimiter position on the tape, to the lastsequence number of the last delimiter position designated by the lastcommand as information on whether or not the files have been written onthe tape up to the designated delimiter position.

For a number of the position designation commands, M (a natural number),and the sequence number of the last written delimiter position on thetape, N (a natural number wherein N<M), the writing control module hasthe sequence number M as indicating the last designated delimiterposition, and notifies the external host of N−M as the relativeposition.

The invention also provides writing control means for a tape recordingapparatus for sequentially recording files when receiving a command towrite the files. The writing control means is for memorizing thedesignated delimiter positions when commands to designate delimiterpositions of files to be written (delimiter position designationcommands) are received.

In one embodiment of the writing control means, when the positiondesignation commands are sequentially received, and also when a command(writing position check commands) to check up to which delimiterposition the files have been written on the tape is received from thehost, the information on whether or not the files have been written onthe tape to the delimiter positions is memorized.

The present invention also provides a writing control method used for atape recording apparatus for sequentially recording files when receivinga command to write files from an external host. In one embodiment, thewriting control method includes temporarily storing the files in abuffer, recording the files on a tape, writing the files stored in thebuffer on the tape, sequentially writing the files stored in the bufferon the tape, and memorizing the designated delimiter positions when acommand (delimiter position designation command) is received from theexternal host, the command designating delimiter positions of the filesto be sequentially written.

The control method further includes notifying the external host ofinformation on whether or not the files have been written on the tape upto the delimiter positions when a command (writing delimiter positioncheck commands) to check up to which delimiter position the files havebeen written on the tape is received from the external host.

BRIEF DESCRIPTION OF THE DRAWINGS

PRIOR ART FIG. 1 is a block diagram of a conventional data archivesystem;

FIG. 2 is a block diagram of a tape drive apparatus;

FIG. 3A shows a writing method of writing from a buffer to a tape in thetape drive;

FIG. 3B shows a timing chart of synchronizing operations of the threefiles to the tape;

FIG. 4 shows a writing sequence (j-1) to (j-4) for collectivelyperforming synchronizing operations (that is, backhitches) of files toreduce time required for the synchronizing operations; and

FIG. 5 illustrates a preferred writing method according to an embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For a more complete understanding of the invention, in the followingdescription reference is made to the accompanying drawings showingcertain embodiments of the invention. However, such followingembodiments are not intended to limit the scope of claims of the presentinvention.

In one embodiment, the invention provides a tape recording apparatus,such as a tape drive, with an improved writing speed, a writing controlof the tape recording apparatus and a writing control method thereof.FIG. 2 shows a block diagram of an example tape drive apparatus 100(also referred to as a tape drive), in accordance with the invention.

In particular, a function to accept two new commands (hereinafterreferred to as “new commands”) is implemented in the tape drive. A firstcommand is an instruction for designation delimiter positions(hereinafter referred to as “a delimiter position designation command”)for indicating delimiter positions of files to be sequentially writtento the tape drive. A second command is an instruction for checking atape writing position (hereinafter referred to as “a writing positioncheck command”) enabling a host to check a delimiter position of thefiles, to which writing of the file on the tape has been completed.These two new commands are used as a pair.

The tape drive apparatus 100 includes a buffer 120, a recording channel130, a writing device (writing module) which may comprise a head 14 b, amagnetic tape medium 14 a, a cartridge 14 e, a motor 150, a data writingcontrol device (writing control module) which may comprise a controller160 and a head position control system 170, and a motor driver 185. Thecontroller 160 receives, through an interface 110, a writing command towrite data (or a record), from the host 105 to the buffer 120, and asynchronous command that instructs to write the data of the buffer 120on the magnetic tape medium 14 a. For example, when the communicationstandard of the interface 110 is a Small Computer System Interface(SCSI), the writing command for writing data or a record from the host105 is a WRITE command. The synchronous command is a WRITE FILEMARKS 0(hereinafter abbreviated as “WRITE FM0”) command for checking that filestemporarily stored (prepared) in the buffer 120 are written on the tape.

The controller 160 controls the tape drive apparatus 100 overall.According to the command received from the host 105, the controller 160performs control of writing and reading the data on/from the magnetictape medium 14 a. The controller 160 further performs control of thehead position control system 170 and the motor driver 185.

The head 14 b writes, on the magnetic tape medium 14 a, the data orrecords passed through the recording channel 130. The magnetic tapemedium 14 a is rolled around reels 14 c and 14 d, and longitudinallymoves, along with rotation thereof, in any one of a direction from thereel 14 c to the reel 14 d and a direction from the reel 14 d to thereel 14 c. The cartridge 14 e is a container housing the reel 14 c,around which the magnetic tape medium 14 a is rolled. A containerhousing the reel 14 d may be provided by use of the same cartridge asthe cartridge 14 e. The motor 150 rotates the reels 14 c and 14 d.

The host 105 checks that a set of data or records, which are temporarilystored in the buffer 120 by the WRITE command, are properly written as afile on the tape. For this check, a synchronous request (Flush) is madeto the tape drive apparatus 100. The data or records written from thehost 105 are temporarily stored in the buffer 120, and the synchronousrequest (Flush) is made by the WRITE FM0 command, so that the data orrecords are properly written on the tape from the buffer. In general,the synchronous request is made after the WRITE command is issued forthe preceding data or records.

FIG. 3A shows a writing-control method using synchronous requests forthree files from a buffer 410 (corresponding to 120 in FIG. 2) in a tapedrive to a tape 420 (corresponding to 14 a in FIG. 2). In a writingcontrol method of the tape drive, when the amount of a series of recordswritten from the host and thus temporarily stored in the buffer 410reaches a certain amount, the records are written on the tape at a speedof the tape drive.

The tape drive is capable of performing write and read operations, andhence, when the amount of records stored in the buffer 410 reaches tosome extent, writing on the tape 420 starts in a manner independent ofthe WRITE command and synchronous command from the host.

In FIG. 3A, synchronous requests are issued in order to write the threefiles A, B and C on the tape 420 which is mounted on the tape drive. Anapplication of the host recognizes each of the files A, B and C havingcontent as a set of records having the content. To check that the filesare properly written on the tape 420, the application of the host issuessynchronous requests (WRITE FM0: when received this command, the tapedrive performs a Flush operation) at delimiter positions of (1), (2) and(3).

When receiving a synchronous request for each of the files A, B and C,the tape drive notifies the application of the host that the files A, Band C designated by the synchronous requests are written on the tape.For example, when synchronization of the file A has been completed, theapplication of the host executes the WRITE command for the next file B,and the file B is temporarily stored in the buffer 420.

FIG. 3B shows a timing chart of synchronizing operations of the threefiles to the tape 420. Backhitches start at the time when thesynchronizing operations of the three files A, B and C to the tape 420are completed. For example, in a case where a synchronous request ismade for the file B following the completion of synchronizing the fileA, the start of the synchronizing operation of the file B is delayedsince a backhitch is intervened in the tape drive. This means that, in acase where synchronous requests are made for all the files, writingperformance overall is reduced.

Even after the writing of the file A on the tape 420 is completed, thetape 420 moves forward in relation to the writing head. In a case wherethe synchronous request for the next file B is made without stopping thetape 420, long wasted space is caused in a recording region between thefile A being written on the tape by the preceding synchronous requestand the file B to be written. To minimize this wasted recordingcapacity, the tape drive sets an interval between the files (records) tobe written in a longitudinal direction of the tape medium to minimum bythe backhitch operation.

The backhitch is executed by the operation of motor drive. Specifically,the tape medium is stopped once with its traveling speed is reduced, andthen reversely moves. After the end position of the tape medium of afile lastly written passes by the writing head, the tape medium is againstopped once with its traveling speed reduced, and then accelerates inthe forward direction to return to a position to be written, therebypositioning the end position of the last file. In a tape drive (LTO,3529, and the like) manufactured by IBM, it takes approximately 2.5 to 3seconds for a backhitch operation of a tape drive caused for eachsynchronous request. The writing of data on the tape associated with anumber of synchronous requests has been a cause to reduce the writingperformance of transfer data from the host since the backhitch operationis frequently performed.

FIG. 3B further shows that although it depends on the size of one file,a writing speed of the file on the tape is approximately several 10msec. One backhitch operation adds, to a time for one writing operation,a time (approximately 3 seconds) on the order of 100 times or morelonger than a writing speed at which a file is written to a tape. Whencompleting the synchronization of the file A, the tape drive needs toperform the backhitch operation. Hence, the tape drive cannot accept thewriting to the tape even when the next file B can be stored in thebuffer 410. FIG. 3B shows that the writing to the tape 420 issubstantially suspended during the backhitch (2 to 3 seconds) even whenthe file B is prepared in the buffer 410.

In a case where three synchronous requests are respectively issued forthe files A, B and C of FIGS. 3A and 3B, the writing performance isreduced for approximately 9 seconds at maximum due to the three times ofthe backhitches. In an example where 100 files are to be written on atape, approximately 300 seconds at least of extra writing time arerequired, in addition to the time originally required for writing thedata, just for the synchronizing operation.

FIG. 4 shows a writing sequence (j-1) to (j-4) where the synchronizingoperations of the files are collectively performed to reduce the timerequired for the synchronizing operations (that is, the backhitches) asmuch as possible. This writing sequence does not make a synchronousrequest for each of files 1, 2 and 3, which is meaningful for anapplication, as a conventional writing sequence does. This is a writingmethod in which at the stage where all the files 1, 2 and 3 are writtenin a buffer of a tape drive 530, the application finally issues asynchronous request (Flush) only once. The writing sequence (j-1) to(j-4) is described in more detail below.

(j-1): is a first state where a backup application 520 residing in thecomputer 210 writes three files 1, 2 and 3 recorded in an HDD 510(corresponding to 220 in FIG. 1), on a tape (corresponding to 240 inFIG. 1) of a tape drive 530 (corresponding to 230 in FIG. 1).

In the following (j-2) to (j-4) sequence, the HDD on which the threefiles are recorded is in common, and thus the description thereof willbe omitted.

(j-2): the backup application 520 stores the files 1, 2 and 3 in thebuffer of the tape drive 530 by WRITE commands.

(j-3): the backup application 520 makes a synchronous request (Flush)once to the tape drive by the WRITE FM0 for the three files 1, 2 and 3stored in the buffer.

(j-4): is a state after making only one synchronous request for writingthe three files, which are meaningful for the backup application, on thetape.

This writing method can limit the time loss to only one backhitch, theperformance problem of the above-described writing method is reduced inthat the reduction of writing performance can be minimized.

For this writing method, because synchronization is performedcollectively, responses to synchronization from the files are delayed,except for the file which is lastly written to the tape drive in termsof individual files. In addition, it cannot be ensured that the filewhich is firstly written to the tape drive is written on the tape untilthe synchronization is completed after the writing of the last file.

In a case where an error of the synchronizing operation is detectedduring the writing of any one of the files 1, 2 and 3 on the tape, thetape drive cannot notify the application that the writing of which filewas in progress when the error occurred. Accordingly, it is necessary toperform rewriting for all the files in the group of files (files 1, 2and 3) to which the writing have been instructed. In terms of the backupapplication, because it is necessary to rewrite all the files, the causeto reduce the writing performance cannot be excluded yet even when thiswriting control method is used.

U.S. Pat. No. 6,839,801, the disclosure of which is hereby incorporatedby reference in its entirety, discloses a technique that data to bewritten from the host is temporarily written on a non-volatile storage.Command completion is immediately returned thereafter in order toprevent the delay of the response performance (the time for thebackhitch operation) for the synchronous request command from the host.An object of this technique is to suppress the reduction of synchronouswriting performance and to improve writing performance. With thistechnique, for the synchronous request from the host, a response isreturned to the data having a high possibility that writing to the tapehas been already completed by a new command of “DEFERRED SYNC”. Thetechnique also provides means for waiting until the completion ofwriting, when the writing of the data on the tape has not been actuallycompleted yet, and thus the synchronization is not completely reduced.In addition, it is not a technique which cheaply uses a tape drive inthat a controller device provided with a DEFERRED SYNC LOGIC andnon-volatile memory are needed.

The writing control of U.S. Pat. No. 6,839,801 contributes to theimprovement of writing performance in that the number of performing thesynchronizing operations, which are a cause of reducing the performance,is cut down. However, when the writing on the tape is performed in thetape drive without using synchronous requests of files, it is impossibleto specify to which delimiter position of the files writing of the fileon the tape has been surely completed.

In the following, a preferred embodiment of the invention is described,which overcomes the drawbacks discussed above with respect to U.S. Pat.No. 6,839,801.

In the flowing description, “a file delimiter position” and “a delimiterposition of a file” mean a delimiter position of a file which isdesignated by an application of a host. It is to be noted that these“positions” do not mean addresses of buffers of files stored in thebuffers in the tape drive. Each file means that records written from thehost is delimited by the application (host). The tape drive simplyperforms sequential writing of the records, and the tape drive per secannot perform writing by recognizing each file.

The application of the host manages a set of records having meaning forthe application. The application intends to perform writing of files ona tape by writing records, but the tape drive per se cannot recognizethe files. Accordingly, in accordance with an embodiment of theinvention, the tape drive is informed of delimiter positions of files bynew commands from the application.

The new commands include two prim functions (for example, a “first newcommand” and a “second new command”).

1. The first new command is sequentially issued by the application atdelimiter positions (“file delimiter positions”) of files (a set ofrecords) at the time of writing the records to let the tape drive toknow file delimiter positions. The tape drive causes the application tomemorize the number of the orders of receiving the first new commands aseach of the file delimiter positions.

2. The second new command is issued by the application to know to whichdelimiter position of the file designated by the first new command thefile has been written on the tape. The tape drive returns to theapplication (host) information of the delimiter position of the lastfile (the tape writing delimiter position) which has been completelywritten on the tape in a case where the delimiters are memorized by thefirst new command. The writing operation of the tape drive is performedon the tape by a sequential writing method. By having this sequentialcharacteristic, even when delimiter positions are designated in advanceby the first new command, and even when tape writing delimiter positionsare present in each of the delimiter positions, the tape drive is onlyneeded to notify the host of only the last tape writing delimiterposition.

For example, suppose a case where, when delimiter positions of the filesare designated for the tape drive by the first new commands, the fileshave been written on the tape to the delimiter position which has beenmemorized N times before counted from “the file delimiter position”which has been already received by the buffer. In other words, the fileshave not yet been written on the tape to the delimiter position whichhas been memorized N−1 times before counted from “the file delimiterposition” which has been already received by the buffer. In this case,the tape drive which has received the second new command from the hostreturns to the host a relative position N from “the file delimiterposition already received by the buffer” as “the file delimiter positionalready written on the tape”. If the last file has already been writtenon the tape, “the file delimiter position already written on the tape”and “the file delimiter position already received by the buffer” are thesame. In this case, the tape drive returns to the host “the filedelimiter position already written on the tape” as the relative position0 from “the file delimiter position already received by the buffer” inresponse to the second new command.

In addition, when a permanent error due to a medium defect of the tape,and the like, is detected, the tape drive returns CHECK CONDITION statusin response to the new command made immediately the detection of theerror. The tape drive receives the first new command designating thefile delimiter position to write the records from the host and to letthe tape drive know the delimiter position of the file. When the secondnew command is received from the host, the tape drive returns “the filedelimiter position already written” indicating that the writing on thetape has been surely completed in the delimiter positions designated ateach time. As a result, it is understood that the application of thehost needs to perform rewriting from the delimiter position of the file,following “the file delimiter position” N which has already been writtenon the tape in which the file has already been written surely by issuingthe second new command.

FIG. 5 shows one embodiment of a data writing control method in the tapedrive according to the present invention. FIG. 5 illustrates a statethat records (distinguished by dotted lines) written by WRITE commandsfrom the application of the host are stored in a buffer 410, and thenwritten on a tape 420. The writing control of the present inventionissues new commands, instead of synchronous request commands WRITE FM0of FIGS. 3A and 3B, at the timing of the delimiter positions (1), (2)and (3) of the files A, B and C having meaning for the application. Thetape drive memorizes the delimiter positions (1), (2) and (3) of filesA, B and C, which are stored in the buffer 410 according to the orderthat the drive receives the new commands (sequence No.: 1, 2 and 3) toperform management of delimiter positions. The tape drive notifies thehost whether the files A, B and C have been written on the tape to thedesignated delimiter positions (1), (2) and (3) by notifying the host ofthe order designating “the tape writing delimiter positions” (1, 2 and3). The delimiter positions (1), (2) and (3) may be memorized by usingmanagement numbers (for example, addresses, blocks and segments) of thebuffer 410 that the drive can obtain. However, the tape drive uses thesequential writing method. Accordingly, it is sufficient for theapplication to obtain the order of writing the files A, B and C, and theapplication does not require detailed values such as addresses of thebuffer. However, in the tape drive, other than the order of receivingthe new commands, or together with the order, the management andmemorization of the file positions may be performed by using thepositions of the buffer (for example, address number of the buffer,segment number of the buffer, or block number of the buffer).

In the writing control in accordance with embodiments of the invention,the writing from the buffer 410 to the tape 420 is not performed by thesynchronous requests from the application of the host. The“asynchronous” writing is performed in the sense that the drive canperform writing on the tape at its own timing. The writing control ofthe present invention depends on the drive timing of the normalsequential writing on the tape of the tape drive, so that the reductionof writing performance can be avoided as much as possible. The tapedrive starts sequentially writing the files (records) stored in thebuffer 410 at a writing speed of its own. The application issues newcommands independently from each WRITE command. The tape drive keepsinformation on whether the files A, B and C whose delimiter positionsare designated by the new commands are written on the tape, and theinformation is conveyed to the application.

FIG. 5 also shows commands to designate delimiters of the files A, B andC in the tape drive at the times of (1), (2) and (3) so as to check upto which delimiter position the files have been written on the tape (afunction of tape writing position check command) is received. In a casewhere it is assumed that the new command issued from the application atthe timing (3) is the tape writing check command designating the file C,when the file C is not written on the tape 420 at that time, then theabove state is notified. In a case where the file A has been alreadywritten, but the files B and C have not been written yet, −2 may bereturned as the relative position of the file A from the file C inresponse to the new command. The application is notified of thisrelative position −2, and hence finds out that the writing on the tapehas been completed to the file A which is in the relative position −2from the position of the last file C of the designated files A, B and C.

In this embodiment, the new commands have both functions of the firstnew command (the delimiter position designation command) and the secondnew command (the writing position check command). The new commandsnotify the tape drive of the delimiter positions of the files to besequentially written (the function of the first new command), and at thesame time, notify the host of information to which delimiter position ofthe file designated by another new command therebefore has been writtenon the tape (the function of the second new command). As describedabove, it is possible to execute the two functions by differentcommands. It is also included in the scope of the present invention thatthe first new command designates the file delimiter positions, and thatthe second new command enables to receive the notification to whichdesignated delimiter position of file the file has been written on thetape.

The writing control method to the tape in the sequential recordingdevice such as the tape drive according to the embodiment of the presentinvention has been disclosed above.

In accordance with embodiments of the invention, when new commands arereceived from the host, the tape drive can make synchronous requests(backhitch operations) unneeded for writing files by notifying whetheror not the designated file has already been written on the tape, so thatthe improvement of writing performance can be achieved.

In addition, in accordance with embodiments of the invention, becausethe delimiter position of the file which has already been written on thetape can be checked by the new commands for a writing error, rewritingthe tape is possible from the file which has not been written yet. As aresult, the performance of writing error processing can be improved.

Furthermore, in accordance with embodiments of the invention, thewriting of each file can be checked, by using the new commands, withoutaccompanying the backhitch operation at each time. Accordingly, theapplication can perform file processing of the files which have alreadybeen written on the tape in parallel with other operations withoutwaiting for checking the writing of the following files on the tape.Thus, the writing performance of the tape drive as a whole, includingthe host, can be improved.

In accordance with embodiments of the invention, the tape drive receivesthe new commands issued by the host, and notifies the host to whichdelimiter position the file have been written on the tape, so thatsynchronous requests can be made unneeded. Consequently, it is possibleto improve the writing performance of files.

It is obvious for those skilled in the art that various modificationsand improvements of the above embodiment can be made, and embodiments towhich the modifications and improvements are made are also included inthe technical scope of the present invention.

Although the preferred embodiment of the present invention has beendescribed in detail, it should be understood that various changes,substitutions and alternations can be made therein without departingfrom spirit and scope of the inventions as defined by the appendedclaims.

1. A tape recording apparatus, for sequentially recording files whenreceiving a command to write the files from an external host,comprising: a buffer for temporarily storing the files; a tape on whichthe files are recorded; a writing device for writing the files stored inthe buffer on the tape; and a writing control device for performingcontrol of sequentially writing the files stored in the buffer on thetape one by one, wherein the writing control device memorizes designateddelimiter positions when delimiter position designation commands arereceived from the external host, the delimiter position designationcommands designating the delimiter positions of the files to besequentially written.
 2. The tape recording apparatus according to claim1, wherein, when the position designation commands are sequentiallyreceived, the writing control device memorizes a number indicating asequence of the receiving command as the designated delimiter positioneach time the command is received.
 3. The tape recording apparatusaccording to claim 1, wherein, when the delimiter position designationcommands are sequentially received, and also when a writing positioncheck command to check up to which delimiter position the files havebeen written on the tape is received, the writing control devicenotifies the external host of information on whether or not the fileshave been written on the tape to the delimiter positions.
 4. The taperecording apparatus according to claim 3, wherein, in response to thewriting position check command, the writing control device notifies theexternal host of a sequence number indicating a last written delimiterposition among the designated delimiter positions to which a file islastly written on the tape, as information on whether or not the fileshave been written on the tape up to the last written delimiter position.5. The tape recording apparatus according to claim 3, wherein, inresponse to the writing position check command, the writing controldevice notifies the external host of a value of a sequence number of thelast written delimiter position on the tape, to a last sequence numberof delimiter positions designated by the last command, as information onwhether or not the files have been written on the tape up to the lastwritten delimiter position.
 6. The tape recording apparatus according toclaim 5, wherein, for a number of the position designation commandsbeing M, wherein M is a natural number, and the sequence number of thelast written delimiter position on the tape being N, wherein N is anatural number and N<M, the writing control device has the sequencenumber M as indicating the last designated delimiter position, andnotifies the external host of N−M as the relative position.
 7. A taperecording system, comprising: a host; and a tape recording apparatusconnected with the host and configured for sequentially recording fileswhen receiving a command to write the files from the host, the taperecording apparatus comprising: a buffer for temporarily storing thefiles; a tape on which the files are recorded; a writing device forwriting the files stored in the buffer on the tape; and a writingcontrol device for performing control of sequentially writing the filesstored in the buffer on the tape one by one, wherein the writing controldevice memorizes designated delimiter positions when delimiter positiondesignation commands are received from the external host, the delimiterposition designation commands designating the delimiter positions of thefiles to be sequentially written, wherein the tape recording apparatusreceives a command issued by the host to write the files, and adelimiter position designation commands for delimiter positions of thefiles.
 8. The tape recording system according to claim 7, wherein thewriting control device memorizes sequence numbers indicating an order ofreceiving the commands as the designated delimiter positions when theposition designation commands are sequentially received.
 9. The taperecording system according to claim 7, wherein, when the positiondesignation commands are sequentially received, and also when a writingposition check command to check up to which delimiter position the fileshave been written on the tape is received from the host, the writingcontrol device notifies the host of information on whether or not thefiles have been written on the tape up to the delimiter positions. 10.The tape recording system according to claim 9, wherein, in response tothe writing position check command, the writing control device notifiesthe host of a sequence number indicating the last written delimiterposition on the tape as information on whether or not the files havebeen written on the tape up to the designated delimiter position. 11.The tape recording system according to claim 9, wherein, in response tothe writing position check command, the writing control device notifiesthe host of a relative value of a sequence number of the last writtendelimiter position on the tape, to the last sequence number of the lastdelimiter position designated by the last command as information onwhether or not the files have been written on the tape up to thedesignated delimiter position.
 12. The tape recording system accordingto claim 11, wherein for a number of the delimiter position designationcommands being M, wherein M is a natural number, and the sequence numberof the last written delimiter position on the tape being N, wherein N isa natural number and N<M, the writing control device has the sequencenumber M as indicating the last designated delimiter position, andnotifies the host of N−M as the relative position.
 13. The taperecording system according to claim 7, wherein the tape is loadable toand unloadable from the tape recording apparatus.
 14. A writing controlmeans, wherein the writing control means is used for a tape recordingapparatus for sequentially recording files when receiving a command towrite the files, and wherein, when delimiter position designationcommands to designate delimiter positions of files to be written arereceived, the designated delimiter positions are memorized.
 15. Thewriting control means according to claim 14, wherein, when the positiondesignation commands are received, and also when a writing positioncheck command, which is used to check up to which delimiter position thefiles have been written on the tape, is received from the host, theinformation on whether or not the files have been written on the tape upto the delimiter position is memorized.
 16. A writing control methodused for a tape recording apparatus for sequentially recording fileswhen receiving a command to write files from an external host, thewriting control method comprising: temporarily storing the files in abuffer; recording the files on a tape; writing the files stored in thebuffer on the tape; sequentially writing the files stored in the bufferon the tape one by one; and memorizing the designated delimiter positionwhen a delimiter position designation command is received from theexternal host, the command designating delimiter position of the filesto be sequentially written.
 17. The writing control method according toclaim 16, further comprising notifying the external host of informationon whether or not the files have been written on the tape up to thedelimiter position when a writing delimiter position check command,which is used to check up to which delimiter position the files havebeen written on the tape, is received from the external host.